1. Field of the Invention
The present invention relates to a call setup method in an Internet Protocol (IP) network and a terminal using the same method.
2. Description of the Related Art
VoIP (Voice over Internet Protocol) means an Internet telecommunication technology in use for devices that transfer voice information via discrete Internet Protocol (IP) packets. Rather than using traditional circuit-committed protocols such as Public Switched Telephone Network (PSTN), VoIP is used to transfer digitalized voice information in discontinuous packets. VoIP uses the real-time protocol (RTP) to help ensure that packets get delivered in a timely manner.
In general, when a new Uniform Resource Locator (URL) is inputted during Internet surfing, a Personal Computer (PC) sends a query message to a Domain Name Service (DNS) server. However, in the case of continuous Internet access to the same URL, previously-received information is first cached in a DNS local table, and matching information is used. That is, the DNS query message is not transmitted.
It is the same for the Address Resolution Protocol (ARP). If an ARP table is stored, in the event of constructing an Ethernet frame for a corresponding IP terminal, Media Access Control (MAC) address information is used on the basis of information existing in the terminal.
On the contrary, various approaches have been considered to reduce call setup time in a Voice over Internet Protocol (VoIP) terminal.
That is, various methods have been sought to quickly search the IP address of a destination terminal on the basis of destination terminal identification (ID) expressed in an initialization message when a call-translating, outbound call manager or outbound proxy server transmits the initiation message at the time of call setup. However, no advanced schemes have been considered for the terminal.
In other words, conventional methods have been focused to find a mapping destination IP address on the basis of network environment and destination ID, but these factors have not been considered for the terminal.
Accordingly, in the case of call setup between IP terminals that interwork with an IP Centrex, conventional schemes of translating addresses through the outbound call manager (or outbound proxy server) encounter gradually increasing load of the outbound call manager without reduction in call setup time.